Systems, devices, and methods for performing trans-abdominal fetal oximetry and/or trans-abdominal fetal pulse oximetry using a fetal heartbeat signal for a pregnant mammal

ABSTRACT

Light reflected from a pregnant woman&#39;s abdomen and fetus contained therein that has been received by a detector and converted into a reflected electronic signal may be received by a processor. A portion of the reflected electronic signal that is reflected from the fetus may be isolated and the isolated portion of the reflected electronic signal may be analyzed to determine a fetal hemoglobin oxygen saturation level of the fetus. The isolation may be achieved by synchronizing the reflected electronic signal with a fetal heartbeat signal and multiplying the synchronized reflected electronic signal by the synchronized fetal heartbeat signal.

RELATED APPLICATIONS

This application is a CONTINUATION of U.S. patent application Ser. No.16/521,431 entitled “SYSTEMS, DEVICES, AND METHODS FOR PERFORMINGTRANS-ABDOMINAL FETAL OXIMETRY AND/OR TRANS-ABDOMINAL FETAL PULSEOXIMETRY USING A FETAL HEARTBEAT SIGNAL FOR A PREGNANT MAMMAL” filed onJul. 24, 2019, which is a CONTINUATION-IN-PART of U.S. patentapplication Ser. No. 15/973,141 entitled “SYSTEMS, DEVICES, AND METHODSFOR PERFORMING TRANS-ABDOMINAL FETAL OXIMETRY AND/OR TRANS-ABDOMINALFETAL PULSE OXIMETRY USING A FETAL HEARTBEAT SIGNAL FOR A PREGNANTMAMMAL” filed on May 7, 2018, which is a CONTINUATION of U.S. patentapplication Ser. No. 15/698,954 entitled “SYSTEMS, DEVICES, AND METHODSFOR PERFORMING TRANS-ABDOMINAL FETAL OXIMETRY AND/OR TRANS-ABDOMINALFETAL PULSE OXIMETRY USING A FETAL HEARTBEAT SIGNAL” filed on Sep. 8,2017, which is a CONTINUATION of U.S. patent application Ser. No.15/393,752 entitled “SYSTEMS, DEVICES, AND METHODS FOR PERFORMINGTRANS-ABDOMINAL FETAL OXIMETRY AND/OR TRANS-ABDOMINAL FETAL PULSEOXIMETRY” filed on Dec. 29, 2016, now U.S. Pat. No. 9,757,058, which isa NON-PROVISIONAL of, and claims priority to, U.S. Provisional PatentApplication No. 62/273,196 entitled “SYSTEMS, DEVICES, AND METHODS FORDETECTING/DETERMINING FETAL HEMOGLOBIN OXYGEN SATURATION LEVELS” filedDec. 30, 2015, all of which are incorporated by reference, in theirentireties, herein.

FIELD OF INVENTION

The present invention is in the field of medical devices and, moreparticularly, in the field of trans-abdominal fetal oximetry andtrans-abdominal fetal pulse oximetry.

BACKGROUND

When a pregnant mammal is engaged in the labor and delivery process forher fetus, a common practice is to monitor both the heart rate of thefetus and the uterine tone of the pregnant mammal. The uterine tone ofthe pregnant mammal provides information regarding the uterinecontractions of the pregnant mammal by measuring the pressure exerted bythe uterine muscle in units of pressure, for example, millimeters ofmercury (mmHg) and/or kilo Pascals (kPg). One way to provide informationregarding the fetal heartbeat and uterine tone to a doctor or otherhealthcare provider is to provide a graph, either in paper or electronicform, that displays a fetal heart rate over time and uterine tone overtime. In most cases, this information is synchronized so that the fetalheartbeat and uterine tone for a particular moment in time may besimultaneously observed. By comparing the fetal heart rate at aparticular moment in time with the uterine tone at that same moment intime, a doctor may be able to determine whether the fetal heart ratedecreases when the pregnant mammal experiences a contraction.

FIGS. 1A and 1B provide two examples of simultaneously displayed fetalheartbeat and uterine tone for corresponding moments in time. In FIGS.1A and 1B, graphs 10A and 10B, respectively, display fetal heartbeat inbeats per minute as a function of time where each vertical line providedon the grid represents one minute. In FIGS. 1A and 1B, graphs 12A and12B, respectively, display uterine tone in mmHg and kPa as a function oftime. In FIG. 1A, graph 10A shows fetal heart rate within a normal rangeof 120-180 beats per minute and there are no obvious fluctuations in thefetal heart rate that correspond with changes in uterine tone. With theinformation provided by FIG. 1A, a doctor may draw the conclusion thatthe fetus is not being negatively impacted by the uterine contractionsand is not in distress. In contrast, graph 10B shows a fetal heart ratethat experiences significant dips (e.g., from approximately 150 beatsper minute prior to a uterine contraction to below 90 beats per minuteduring an immediately following a uterine contraction) that correspondwith uterine contractions (i.e., increases in pressure within theuterus). With the information provided by FIG. 1B, a doctor may draw theconclusion that the fetus is being negatively impacted by the uterinecontractions and may be in distress (e.g., experiencing a lack of oxygenthat may cause neurologic damage). Upon drawing this conclusion, thedoctor may decide that the fetus' health is in danger and, therefore, itshould be surgically removed from the uterus via a Caesarian section(C-section). However, a change in fetal heart rate of the type shown inFIG. 1B does not always indicate that the fetus is in distress as thereare many other possible causes for a drop in fetal heart rate. Thus, thedoctor may prescribe a C-section when one is not needed causing undueharm to the pregnant mammal.

Oximetry is a method for determining the oxygen saturation of hemoglobinin a mammal's blood. Typically, 90% (or higher) of an adult human'shemoglobin is saturated with (i.e., bonded to) oxygen while only 30-60%of a fetus's blood is saturated with oxygen.

Pulse oximetry is a type of oximetry that uses changes in arterial bloodvolume through a heartbeat cycle to internally calibrate oxygensaturation measurements of the oxygen level of the blood.

Current methods of performing fetal oximetry are flawed for manyreasons. For example, while U.S. Patent Publication No. 2004/0116789describes a fetal oximeter using pulse oximetry, this oximeter is flawedfor at least three reasons. First, the wavelengths of theelectro-magnetic radiation used by the '789 Publication to determinefetal oximetry are short and consequently cannot travel a distancethrough the abdomen of the pregnant mammal so as to reach the fetus withsufficient strength. Thus, the signal reflected signal is too weak todecipher. Second, the '789 Publication is flawed because of theassumptions included therein are based on research with adulthemoglobin, which is fundamentally different from fetal hemoglobinbecause fetal hemoglobin has a different structure than adult hemoglobinand therefore absorbs/reflects light differently. Finally, the '789application does not process the received signal to reduce noise.

Like the '789 Publication, Patent WO 2009032168 describes a fetaloximeter using near-infrared spectroscopy but fails to provide a signalprocessing algorithm. In addition, the WO 2009032168 uses assumptionsregarding adult hemoglobin to determine fetal oximetry, which yieldsinaccurate results because, as noted above, fetal hemoglobin and adulthemoglobin have different structures and, therefore reflect lightdifferently.

U.S. Patent Publication No. 2011/0218413 describes an algorithm forsignal processing that uses maternal electrocardiography (ECG), Doppler,and pulse oximetry. However, for at least the reasons pointed out above,trying to obtain a fetal oximetry signal using maternal (i.e., adult)pulse oximetry won't work. Furthermore, the '413 Publication fails tomake any compensation for structural differences in fetal and adulthemoglobin.

U.S. Patent Publication No. 2011/0218413 provides another examplewherein a pregnant mammal wears a belt that shines light towards thebelly and fetus that is detected on the other side of the abdomen. Thedistance traveled by the light would be 15-30 inches, or 35 to 75 cm,and this is not technically feasible because the signal received by thedetector would be too weak to decipher. The light loses intensityquickly and there are FDA limitations on how intense the light directedinto a pregnant mammal's abdomen can be because light that is toointense could cause, for example, burns to the pregnant mammal andretinal damage to the fetus.

SUMMARY

Disclosed herein are systems, devices, and methods for performingtrans-abdominal fetal oximetry and/or trans-abdominal fetal pulseoximetry. The systems, devices, and methods may be performed using oneor more fetal hemoglobin probes that are in contact with an abdomen ofpregnant mammal (i.e., attached to the pregnant mammal via an adhesive,strap, harness, etc.). In some embodiments, all, or a portion of, afetal hemoglobin probe may not be in contact with the pregnant mammal'sabdomen as may be the case when performing a contactless pulse oximetrymeasurement and calculation. When a contactless pulse oximetrymeasurement and calculation is used, fetal hemoglobin probe and/or partsthereof may be positioned above the pregnant mammal's abdomen on, forexample, a scaffold or cart.

Exemplary fetal hemoglobin probes disclosed herein may include ahousing, a plurality of light sources, one or more detectors, atransceiver, and a power source. Exemplary systems disclosed hereininclude one or more fetal hemoglobin probes and a processor or computerthat may be coupled with a display device (e.g., monitor or touchscreen). More particularly, the housing of a fetal hemoglobin probe maybe configured to house a first light source, a second light source, adetector, a transceiver, and a power source. In some cases the housing,first light source, second light source, detector, transceiver, and/orpower source are configured to be disposable following a single use.

The first light source adapted to project light of a first wavelengthinto the abdomen of a pregnant mammal toward a fetus contained thereinand the second light source adapted to project light of a secondwavelength into the abdomen of the pregnant mammal toward the fetus. Insome instances, the first and second light sources may reside in asingle light housing configured with multiple light sources (e.g., LEDs)and, in other instances, the first and second light sources may beseparately housed. Exemplary wavelengths for light emitted from thefirst light source may be between 700 nm and 740 nm and exemplarywavelengths for light emitted from the second light source may bebetween 800 and 900 nm.

The detector may be adapted to detect light reflected from the pregnantmammal's abdomen and the fetus. Exemplary detectors include but are notlimited to photo detectors, light sensors, photodiodes and cameras. Whenthe detector is a photo detector (or the like) the detector may alsoconvert the detected light into an electronic reflected signal andcommunicate the electronic reflected signal to the transceiver.

The transceiver may be adapted to receive the electronic reflectedsignal from the detector and communicate the received electronicreflected signal to a processor or computer. The transceiver may be anydevice capable of receiving information from the detector andcommunicating information from the fetal hemoglobin probe.

The power source may be electrically coupled to the first light source,the second light source, and the detector and adapted to provideelectrical power to first light source, the second light source, thedetector, and the transceiver. Exemplary power sources include, but arenot limited to, batteries and equipment to couple the fetal hemoglobinprobe to a conventional power source (e.g., wall socket).

The processor may be configured to receive the electronic reflectedsignal from the detector and isolate a portion of the reflectedelectronic signal that is reflected from the fetus. The processor maythen analyze the isolated portion of the reflected electronic signal todetermine a fetal hemoglobin oxygen saturation level and provide anindication of the oxygen level of fetal blood to a display device, suchas a monitor.

In some embodiments, the system may include an adjustment mechanismcoupled to at least one of the first and second light sources. Theadjustment mechanism may be adapted to adjust, for example, a frequencyof light emitted by the respective first and/or second light sources, anincident angle of the light emitted by the respective first and/orsecond light sources when projected into the pregnant mammal's abdomen,and focus a beam of light as it is projected into the pregnant mammal'sabdomen as it emitted from the respective first and/or second lightsources.

In one exemplary embodiment, the system further includes an adjustmentdevice coupled to the housing, or a portion thereof. The adjustmentdevice may be adapted to adjust, for example, a frequency of lightemitted by the respective first and second light sources, an incidentangle of the light emitted by the respective first and/or second lightsources when projected into the pregnant mammal's abdomen, and focus abeam of light as it is projected into the pregnant mammal's abdomen asit emitted from the respective first and/or second light sources.

In some embodiments, the system may include an additional detector, theadditional detector may be positioned within the housing and coupled tothe transceiver and power source. The additional detector may be adaptedto detect light reflected from the pregnant mammal's abdomen and thefetus, convert the detected light into an additional electronicreflected signal, and communicate the additional electronic reflectedsignal to the transceiver and/or processor or a computer.

In some embodiments, the system and/or fetal hemoglobin probe mayinclude four or more additional light sources housed within the housing,or housed in a separate housing. Each of the additional light sourcesbeing coupled to a power source. These embodiments may also include anadditional detector. The additional detector may be positioned withinthe housing and coupled to the transceiver and power sources and may beadapted to detect light reflected from the pregnant mammal's abdomen andthe fetus, convert the detected light into an additional electronicreflected signal, and communicate the additional electronic reflectedsignal to the transceiver and/or processor or a computer. In theseembodiments, the housing may be adapted to have a length of at least 10cm so as to extend around a portion of the pregnant mammal's abdomen anddirect light at multiple positions (e.g., two or more sides) of thefetus. In these embodiments, the detector may be positioned on a firstside of the housing and the additional detector may be positioned on asecond side of the housing and the light sources are positioned betweenthe first and second sides of the housing.

In some cases, the system may include a temperature probe housed withinthe housing and coupled to the power supply and transceiver. Thetemperature probe may be adapted to measure a temperature of thepregnant mammal's abdomen and/or skin and communicate the temperaturemeasurements to, for example, the transceiver and/or controller. Attimes, a temperature measurement in excess of a threshold may indicatethat the system is too hot and may cause injury to the pregnant mammaland/or fetus. When this happens, controller may shut off one or morecomponents of the system and/or notify an operator of the pregnantmammal's elevated temperature.

In another embodiment, the system may include an ultrasonic detectorbeing housed within the housing and coupled to the power supply andtransceiver. The ultrasonic detector may be adapted to detect ultrasonicemissions of the pregnant mammal's abdomen and fetus caused by transientthermoelastic expansion resultant from an interaction of the pregnantmammal's abdomen and the fetus' tissue to light emitted from at leastone of the first light source and the second light source due to theso-called photoacoustic effect.

In another embodiment, the system may further include a uterinecontraction measurement that is housed within the housing and coupled tothe power supply and transceiver, processor, and/or a computer. Theuterine contraction measurement may be adapted to measure changes in amuscular state of the pregnant mammal's uterus and communicate thesemeasurements to the transceiver, the processor, and/or a computer.

Exemplary methods described herein may include directing, by a lightsource, a light beam emitted from the light source into an abdomen of apregnant mammal toward a fetus contained therein. Light reflected by thepregnant mammal and the fetus may be received at a detector over a firsttime domain. The detector may then convert the received light into anelectronic reflected signal and communicate the electronic reflectedsignal to a computer/processor.

The computer may then process the electronic reflected signal to isolatea portion of the electronic reflected signal reflected from the fetusand analyze the portion of the electronic reflected signal reflectedfrom the fetus to determine a fetal hemoglobin oxygen saturation levelof the fetus. The computer may then facilitate provision of anindication of the fetal hemoglobin oxygen saturation level to anoperator, such as a doctor or medical technician.

In some embodiments, processing the electronic reflected signal toisolate a portion of the electronic reflected signal reflected from thefetus includes receiving a heartbeat signal for the pregnant mammal overa second time domain. The heartbeat signal indicates when, in the secondtime domain, a pregnant mammal's heartbeat occurs. The electronicreflected signal and the pregnant mammal's heartbeat signal may then besynchronized over the first time domain and the second time domain and aportion of the electronic received signal that corresponds in thesynchronized first and second time domains with the heartbeat signal forthe pregnant mammal may be determined. The portion of the electronicreceived signal that corresponds with the heartbeat signal for thepregnant mammal from the electronic received signal may then besubtracted electronic received signal.

In another embodiment, the processing of the electronic reflected signalto isolate a portion of the electronic reflected signal reflected fromthe fetus may include receiving a fetal heartbeat signal for the fetusover a second time domain. The fetal heartbeat signal may indicate when,in the second time domain, a fetal heartbeat occurs. The electronicreflected signal and the fetal heartbeat signal may then be synchronizedover the first time domain and the second time domain and portions ofthe electronic reflected signal that correspond in the synchronizedfirst and second time domains with individual heartbeats of the fetus asindicated by the received heartbeat signal for the fetus may be examinedto determine the fetal hemoglobin saturation level of the fetus.

In a further embodiment, processing the electronic reflected signal toisolate a portion of the electronic reflected signal reflected from thefetus comprises receiving a fetal heartbeat signal for the fetus over asecond time domain, the heartbeat signal indicating when, in the secondtime domain, a fetal heartbeat occurs. The electronic reflected signaland the fetal heartbeat signal might then be synchronized over the firsttime domain and the second time domain. Then, the synchronizedelectronic reflected signal may be multiplied by the synchronized fetalheartbeat signal.

BRIEF DESCRIPTION OF THE FIGURES

The present invention is illustrated by way of example, and notlimitation, in the figures of the accompanying drawings in which:

FIGS. 1A and 1B provide examples of simultaneously displayed fetalheartbeat and uterine tone for corresponding moments in time.

FIG. 2A provides an exemplary system 100 for determining a fetal oxygenlevel, consistent with an embodiment of the invention;

FIGS. 2B-2E provide block diagrams of exemplary fetal hemoglobin probes,consistent with embodiments of the invention;

FIGS. 3A, 3B, 3C, and 3D provide illustrations of how light from a fetalhemoglobin probe may be directed into a pregnant mammal's abdomen,consistent with embodiments of the invention;

FIG. 4A is a flowchart illustrating a process for determining fetalhemoglobin saturation level, consistent with embodiments of theinvention;

FIGS. 4B and 4C are flowcharts illustrating processes for processing thereflected electronic signal to isolate the portion of the reflectedelectronic signal reflected from the fetus, consistent with embodimentsof the invention;

FIG. 5A provides a graph of total reflected electronic signal intensityvs. time, consistent with an embodiment of the invention;

FIG. 5B provides a graph of a fetal Doppler signal vs. time, consistentwith an embodiment of the invention;

FIG. 5C provides a graph that shows the product of multiplying the totalreflected electronic signal intensity and the Doppler signal togetherwhile synchronizing over time, consistent with an embodiment of theinvention;

FIG. 5D, provides a graph of the total reflected electronic signalintensity, the fetal heartbeat/Doppler signal and the result ofmultiplying total reflected electronic signal intensity and Dopplersignal synchronized over time, consistent with an embodiment of theinvention;

FIG. 6A provides a graph of a fetal Doppler signal vs. time, consistentwith an embodiment of the invention;

FIG. 6B provides a graph of reflected electronic signal intensity for λ₁vs. time, consistent with an embodiment of the invention;

FIG. 6C provides a graph that shows the product of multiplying the totalreflected electronic signal intensity for λ₁ and the fetal Dopplersignal together while synchronizing over time, consistent with anembodiment of the invention;

FIG. 6D, provides a graph that shows the product of multiplying thetotal reflected electronic signal intensity for λ₁ and the fetal Dopplersignal together while synchronizing over time averaged over severalperiods, consistent with an embodiment of the invention;

FIG. 6E provides a graph of reflected electronic signal intensity for λ₂vs. time, consistent with an embodiment of the invention;

FIG. 6F provides a graph that shows the product of multiplying the totalreflected electronic signal intensity for λ₂ and the fetal Dopplersignal together while synchronizing over time, consistent with anembodiment of the invention;

FIG. 6G, provides a graph that shows the product of multiplying thetotal reflected electronic signal intensity for λ₂ and the fetal Dopplersignal together while synchronizing over time averaged over severalperiods, consistent with an embodiment of the invention;

FIG. 6H provides a graph that shows a relationship between a red/IRwavelength modulation ration and arterial oxygen saturation (% SaO2);

FIG. 7A provides a table of various hemoglobin measurements as afunction of light wavelength shone into the blood of an adult donor andfetal blood obtained by puncture of the umbilical cord immediately afterdelivery, consistent with an embodiment of the invention;

FIG. 7B depicts a graph that shows difference in absorptivities betweenoxygenated and deoxygenated state of fetal and the pregnant woman'shemoglobin in visible wavelengths of light, consistent with anembodiment of the invention;

FIG. 7C depicts a graph that shows difference in absorptivities betweenoxy- and deoxy-state of fetal and the pregnant woman's hemoglobin in thenear infrared (NIR) wavelengths of light, consistent with an embodimentof the invention;

FIG. 8A provides an exemplary display that provides a level of fetalhemoglobin oxygen saturation along with other information regardingmeasurements of the pregnant mammal and fetus, consistent with anembodiment of the invention; and

FIG. 8B provides an exemplary display of synchronized fetal heartbeat,fetal hemoglobin oxygen saturation rate, and uterine tone forcorresponding moments in time, consistent with an embodiment of theinvention.

Throughout the drawings, the same reference numerals and characters,unless otherwise stated, are used to denote like features, elements,components, or portions of the illustrated embodiments. Moreover, whilethe subject invention will now be described in detail with reference tothe drawings, the description is done in connection with theillustrative embodiments. It is intended that changes and modificationscan be made to the described embodiments without departing from the truescope and spirit of the subject invention as defined by the appendedclaims.

DESCRIPTION

Described herein are systems, devices, and methods for fetal oximetryand/or fetal pulse oximetry both trans-abdominally and in-utero. A keyoutput of fetal oximetry and/or fetal pulse oximetry is the level ofoxygen saturation of the fetus's blood (also referred to herein as“fetal hemoglobin oxygen saturation level” and “oxygen saturationlevel”, which may also be understood as the percentage of hemoglobinpresent in the fetus' blood that is bound to oxygen. The oxygensaturation level of a fetus' blood may be used by trained medicalprofessionals to assess the health of a fetus as well as a level ofstress it may be under during, for example, a labor and deliveryprocess. Typically values of oxygen saturation for fetal blood fallwithin the range of 30-60% with anything lower than 30% indicating thatthe fetus may be in distress.

For the purposes of the following discussion, the terms “pregnantmammal” or “maternal” “mother” is used to refer to female human being oranimal (e.g., horse or cow) pregnant with a fetus. In most embodiments,the pregnant individual will be a human being but this need not be thecase as the invention may be used for nearly any pregnant mammal.Whether, or not, the pregnant mammal is the biological mother of thefetus (i.e., source of the egg from which the fetus grows) is notrelevant to this invention. What is relevant is that the woman ispregnant with the fetus.

Typically, fetal wellbeing is assessed during labor and delivery bylooking at the absolute fetal heart rate as measured in beats per minuteand observing how fetal heart rate changes, or reacts to, uterinecontractions. It is generally accepted that a fetal heart rate withinthe range of 120-160 beats per minute is normal and does not indicatefetal distress. However, sudden changes in fetal heart rate as well asfetal heart rates that are too high (e.g., 180 beats per minute) or toolow (e.g., 100 or 80 beats per minute) are cause for concern, especiallyif these changes occur during a prolonged, difficult, or otherwisecomplicated labor and delivery process.

For example, as the uterus contracts to expel the baby out of the birthcanal, the contracting uterus constricts the blood vessels and henceblood flow to and from the placenta, which supplies blood to and fromthe fetus. It is expected that restricted blood flow to the fetus mayresult in a slowing of the fetal heart rate. However, a drop in fetalheart rate from 150 to 120 after every uterine contraction may be anindication of fetal distress and may prompt intervention (e.g., aC-section, drug administration, etc.) by a physician or other clinicianduring the birthing process.

However, in some instances, this intervention may not be necessarybecause not all drops in fetal heart rate are caused by fetal distress.In fact, the fetus is frequently just fine when its heart ratechanges—but the physician has no further information to assist indetermining whether the change in fetal heart rate is normal orpathological. Thus, an indication of the oxygen saturation level of thefetus' hemoglobin would be a useful additional indication of fetalwellbeing when, for example, determining whether to intervene in thelabor and delivery process with surgery or other treatmentadministration. For example, an indication that the fetal hemoglobinoxygen saturation level is constant provides an indication to thephysician that the fetus is in good health even when the heart rate ofthe fetus drops or changes. Conversely, a drop in the fetal hemoglobinoxygen saturation level following uterine contractions coupled with adecreasing heart rate would be a cause for concern and may indicate tothe physician that an intervention, like a C-section, is necessary.

Currently, many C-sections are performed solely because of variationsin, or drops of, fetal heart rate, which are seen by physicians as asign of fetal distress. 2 million C-sections are performed annually inthe United States and, in some regions of the United States, C-sectionsare performed in nearly half (50%) of all births. In some instances,these C-sections may not be necessary because the fetus may not truly bein distress. However, without further information (as may be providedvia fetal pulse oximetry), physicians may over-prescribe C-sections andother interventions out of an abundance of caution

The present invention provides a more complete picture of fetal healthduring the labor and delivery process and may thereby reduce the numberof unnecessarily performed C-sections when the decision to perform aC-section is based on fetal heart rate readings alone. It is expectedthat reducing the number of unnecessarily performed C-sections willreduce the overall cost of health care for pregnant women and newbornsand reduce the number of complications that result from C-sections,which can be very significant. For example, 1 in 1000 C-sections willresult in a major complication such as a blood clot, requirement of ablood transfusion, or surgical wound infection and 1 in 10,000C-sections will result in death of the mother.

Fetal hemoglobin has a structure that is slightly different from thestructure hemoglobin of adult hemoglobin. More specifically, adulthemoglobin has 2 alpha and 2 beta polypeptide chains and fetalhemoglobin has 2 alpha and 2 gamma polypeptide chains. Additionally,fetal hemoglobin has a stronger affinity for oxygen than adulthemoglobin. Because of these factors, fetal hemoglobin absorbs lightdifferently than maternal hemoglobin.

Additionally, fetal hemoglobin has a conformation when bound to oxygenthat is different from the conformation of the fetal hemoglobin whenunbound to oxygen. These different conformations of the hemoglobinabsorb light at different amounts and hence reflect light at differentamounts. Therefore, observation of fetal venous hemoglobin oxygensaturation levels may be clinically more useful than fetal arterialhemoglobin oxygen saturation levels.

Disclosed herein are systems, devices, and methods for performingnon-invasive in-utero fetal oximetry using near infrared spectroscopy(NIRS) to determine the oxygen saturation level of arterial and/orvenous fetal hemoglobin. The determined oxygen saturation level ofarterial and/or venous fetal hemoglobin may then be used by, forexample, a physical or other caregiver to ascertain informationregarding fetal health and/or distress. In some embodiments, thesystems, devices, and methods may employ a non-invasive monitor that canbe placed on a pregnant mammal's abdomen to monitor fetal oxygensaturation levels.

Because fetal hemoglobin is microscopic, it cannot be observed directly.However, reflections of near infrared light from the fetal hemoglobinmay be observed. Furthermore, different intensities for differentwavelengths of light that are reflected by the fetal hemoglobin may alsobe observed. Additionally, different intensities for light that isreflected by fetal oxyhemoglobin when compared to fetal de-oxyhemoglobinmay also be observed. Processing of this observed reflected light mightyield a determination of a fetal oxygen saturation level.

FIG. 2A provides an exemplary system 100 for determining a fetal oxygenlevel and, in some instances, detecting and/or determining fetalhemoglobin oxygen saturation levels. The components of system 100 may becoupled together via wired or wireless communication links. In someinstances wireless communication of one or more components of system 100may be enabled using short-range wireless communication protocolsdesigned to communicate over relatively short distances (e.g.,BLUETOOTH® near field communication (NFC), radio-frequencyidentification (RFID), and Wi-Fi) with, for example, a computer orpersonal electronic device as described below. In some embodiments, oneor more components of system 100 may include one or more devicesconfigured to communicate via one or more short-range communicationprotocols (e.g., near field communication (NFC), Bluetooth,Radio-frequency identification (RFID), and Wi-Fi).

System 100 includes a number of independent sensors/probes designed tomonitor various aspects of maternal and/or fetal health and be incontact with a pregnant mammal. These probes/sensors are a fetalhemoglobin probe 115, a NIRS adult hemoglobin probe 125 a pulse oximetryprobe 130, and a Doppler and/or ultrasound probe 135. In someembodiments, system 100 may also include an electrocardiography (EKG, orECG) machine (not shown) that may be used to determine the pregnantmammal's and/or fetus' heart rate and/or an intrauterine pulse oximetryprobe that may be used to determine the fetus' heart rate. The Dopplerand/or ultrasound probe 135 may be configured to be placed on theabdomen of the pregnant mammal and may be of a size and shape thatapproximates a silver U.S. dollar coin. Pulse oximetry probe 130 may bea conventional pulse oximetry probe placed on pregnant mammal's handand/or finger to measure the pregnant mammal's oxygen saturation. NIRSadult hemoglobin probe 125 may be placed on, for example, the pregnantmammal's 2nd finger and may be configured to, for example, use nearinfrared spectroscopy to calculate the ratio of adult oxyhemoglobin toadult de-oxyhemoglobin. NIRS Adult hemoglobin probe 125 may also be usedto determine the pregnant mammal's heart rate.

Optionally, system 100 may include a uterine contraction measurementdevice 140 configured to measure the strength and/or timing of thepregnant mammal's uterine contractions. In some embodiments, uterinecontractions will be measured by uterine contraction measurement device140 as a function of pressure (measured in e.g., mmHg) over time. Insome instances, the uterine contraction measurement device 140 is and/orincludes a tocotransducer, which is an instrument that includes apressure-sensing area that detects changes in the abdominal contour tomeasure uterine activity and, in this way, monitors frequency andduration of contractions.

In another embodiment, uterine contraction measurement device 140 may beconfigured to pass an electrical current through the pregnant mammal andmeasure changes in the electrical current as the uterus contracts.Additionally, or alternatively, uterine contractions may also bemeasured via near infrared spectroscopy because uterine contractions,which are muscle contractions, are oscillations of the uterine musclebetween a contracted state and a relaxed state. Oxygen consumption ofthe uterine muscle during both of these stages is different and thesedifferences may be detectable using NIRS.

Measurements from NIRS adult hemoglobin probe 125, pulse oximetry probe130, Doppler and/or ultrasound probe 135, and/or uterine contractionmeasurement device 140 may be communicated to receiver 145 forcommunication to computer 150 and display on display device 155. In someinstances, one or more of NIRS adult hemoglobin probe 125, pulseoximetry probe 130, a Doppler and/or ultrasound probe 135, uterinecontraction measurement device 140 may include a dedicated display thatprovides the measurements to, for example, an operator or medicaltreatment provider.

As will be discussed below, measurements provided by NIRS adulthemoglobin probe 125, pulse oximetry probe 130, a Doppler and/orultrasound probe 135, uterine contraction measurement device 140 may beused in conjunction with fetal hemoglobin probe 115 to isolate a fetalpulse signal and/or fetal heart rate from a maternal pulse signal and/ormaternal heart rate.

It is important to note that not all of these probes may be used inevery instance. For example, when the pregnant mammal is using fetalhemoglobin probe 115 in a setting outside of a hospital or treatmentfacility (e.g., at home or work) then, some of the probes (e.g., NIRSadult hemoglobin probe 125, pulse oximetry probe 130, a Doppler and/orultrasound probe 135, uterine contraction measurement device 140) ofsystem 100 may not be used.

Receiver 145 may be configured to receive signals and/or data from oneor more components of system 100 including, but not limited to, fetalhemoglobin probe 115, NIRS adult hemoglobin probe 125, pulse oximetryprobe 130, Doppler and/or ultrasound probe 135, and/or uterinecontraction measurement device 140. Communication of receiver 145 withother components of system may be made using wired or wirelesscommunication.

In some instances, receiver 145 may be configured to process orpre-process received signals so as to, for example, make the signalscompatible with computer 150 (e.g., convert an optical signal to anelectrical signal), improve SNR, amplify a received signal, etc. In someinstances, receiver 145 may be resident within and/or a component ofcomputer 150. Also, while receiver 145 is depicted in FIG. 2A as asingle receiver, that is not necessarily the case as any number ofappropriate receivers (e.g., 2, 3, 4, 5) may be used to receive signalsfrom system 100 components and communicate them to computer 150. In someembodiments, computer 150 may amplify or otherwise condition thereceived reflected signal so as to, for example, improve thesignal-to-noise ratio.

Receiver 145 may communicate received, pre-processed, and/or processedsignals to computer 150. Computer 150 may act to process the receivedsignals, as discussed in greater detail below, and facilitate provisionof the results to a display device 155. Exemplary computers 150 includedesktop and laptop computers, servers, tablet computers, personalelectronic devices, mobile devices (e.g., smart phones), and so on.Exemplary display devices 155 are computer monitors, tablet computerdevices, and displays provided by one or more of the components ofsystem 100. In some instances, display device 155 may be resident inreceiver 145 and/or computer 150.

Fetal hemoglobin probe 115 may be used to direct NIR light into theabdomen of the pregnant mammal so as to reach the fetus and to detectlight reflected from the fetus. The NIR light may be emitted by fetalhemoglobin probe 115 in, for example, a continuous and/or pulsed manner.This reflected light might then be processed in order to determine howmuch light, at various wavelengths, is reflected and/or absorbed by thefetal oxyhemoglobin and/or de-oxyhemoglobin so that a fetal hemoglobinoxygen saturation level may be determined. This processing will bediscussed in greater detail below. In some embodiments, fetal hemoglobinprobe 115 may be configured, partially or wholly, as a single-use, ordisposable, probe that is affixed to the pregnant mammal's skin on, forexample, the pregnant mammal's abdomen and, in some embodiments, in thesupra-pubic (bikini) region.

Exemplary dimensions for fetal hemoglobin probe 115 include, but are notlimited to, 2-16 inches in length and 0.5-8 inches in width. In someinstances, fetal hemoglobin probe 115 may come in a variety of sizes soas to, for example, accommodate varying clinical needs, the size of thefetus, fetal position, the size of the pregnant mammal, and/or the sizeof the pregnant mammal's abdomen.

Fetal hemoglobin probe 115 may include one or more components as will bedescribed in greater detail below with regard to FIGS. 2B-2E, of whichthe fetal hemoglobin probes of FIG. 2B-2D (i.e., 115A, 115B, 115C, and115D) are trans-abdominal fetal hemoglobin probes. The fetal hemoglobinprobes 115 disclosed herein may include a housing 102 configured tohouse one or more components of fetal hemoglobin probe 115. Although theembodiments disclosed herein have all of the components of fetalhemoglobin probes 115 contained within a single housing 102, this is notnecessarily the case as, for example, two or more components of a fetalhemoglobin probe 115 may be housed in separate housings 102. Housings102 may be, for example, square, circular, or rectangular in shape andmay be designed to be, in some instances, adjustable depending on, forexample, a topology of the pregnant mammal's abdomen, a level of skinpigmentation for the pregnant mammal and/or her fetus, and so on.

In some embodiments, fetal hemoglobin probe 115 and/or housing 102 maybe disposable and in other embodiments, fetal hemoglobin probe 115(including and/or housing 102) may be configured for multiple uses(i.e., reusable). In some embodiments, (e.g., when fetal hemoglobinprobe is configured to be disposable), may include an adhesive designedto be applied to the skin of the pregnant mammal's abdomen (e.g., glue,tape, etc.) configured to apply housing 102/fetal hemoglobin probe 115directly to the skin of the pregnant mammal's abdomen and hold it inplace there in a manner similar to a sticker. In some instances, thefetal hemoglobin probe 115 may be applied to the pregnant mammal's skinvia tape or a strap that cooperates with a mechanism (e.g., snap, loop,etc.) (not shown) provided by the housing 102. In some circumstances,housing 102 may be attached/adjacent to the pregnant mammal's skin sothat it does not move and, in other instances, it may be allowed to movein order to, for example, attain better measurements/readings. In somecases, housing 102 and/or a portion thereof may not be adapted to be incontact with the pregnant mammal's abdomen.

In some embodiments, housing 102 and/or a portion thereof may cooperatewith a reusable and/or disposable sleeve (not shown) that fits overfetal hemoglobin probe 115 so that fetal hemoglobin probe 115 may beplaced within a housing 102 reusable and/or disposable sleeve so that itmay be applied to the pregnant mammal's skin.

Fetal hemoglobin probe 115 may be adapted to direct, or shine, light ofone or more wavelengths into the abdomen of a pregnant mammal andreceive a signal corresponding to a reflection of a portion of thatlight from the pregnant mammal's tissue and fluid as well as the tissueand fluids of the fetus.

Optionally, fetal hemoglobin probe 115 may include one or moremechanisms that enable the emitted light to be directed in a particulardirection. Such mechanisms include, but are not limited to, wedges oradhesive material, that may be transparent or substantially transparent.For example, a fetal hemoglobin probe 115 may include a wedge positionedon one side that operates to direct the light in a particular directionrelative to the surface of the pregnant mammal's skin and/or position adetector or transceiver to receive an optimized amount of reflectedlight.

In some embodiments, a fetal hemoglobin probe 115 may be adapted to beworn by a pregnant mammal for an extended period of time (e.g., days,weeks, etc.) that is not necessarily coincident with the labor anddelivery process in order to, for example, monitor the health of afetus. In some embodiments, one or more components of fetal hemoglobinprobe 115 may be positioned outside the fetal hemoglobin probe 115 andmay be optically connected thereto via, for example, one or more fiberoptic or Ethernet cable(s).

A fetal hemoglobin probe 115 may be of any appropriate size and, in somecircumstances, may be sized so as to accommodate the size of thepregnant mammal using any appropriate sizing system (e.g., waist sizeand/or small, medium, large, etc.). Exemplary lengths for a fetalhemoglobin probe 115 include a length of 4 cm-40 cm and a width of 2cm-10 cm. In some circumstances, the size and/or configuration of afetal hemoglobin probe 115, or components thereof, may be responsive toskin pigmentation of the pregnant mammal and/or fetus.

It will be understood that although the components of fetal hemoglobinprobe 115 are described herein as being included in a single probe, thatis not necessarily so as the components of fetal hemoglobin probe 115may be present in two or more different objects/devices applied to apregnant mammal. In some instances, more than one fetal hemoglobin probe115 may be used so as to, for example, improve accuracy of the fetaloxygen saturation measurement. For example, a first fetal hemoglobinprobe 115 (or a component thereof) may be placed on a left side of apregnant mammal's abdomen and a second fetal hemoglobin probe 115 (or acomponent thereof) may be placed on a right side of the pregnantmammal's abdomen.

In some embodiments, fetal hemoglobin probe 115 and/or a pregnant mammalwearing a fetal hemoglobin probe 115 may be electrically insulated fromone or more components of system 100 by, for example, an electricityisolator 120. Exemplary electricity insulators 120 include circuitbreakers, ground fault switches, and fuses.

Turning now to FIGS. 2B-2E, which show different embodiments ofexemplary fetal hemoglobin probes 115 labeled as 115A, 115B, 115C, and115D, respectively, intended to be used trans-abdominally. It will beunderstood that reference to fetal hemoglobin probe 115 made herein mayalso refer to, and include, other embodiments of fetal hemoglobin probeincluding fetal hemoglobin probe 115A, fetal hemoglobin probe 115B,fetal hemoglobin probe 115C, and fetal hemoglobin probe 115D. FIG. 2Billustrates exemplary fetal hemoglobin probe 115A, which includes apower supply 160, light source(s) 105, a transceiver 107, and a detector114.

Exemplary power supplies 160 include an on-board battery and/or anelectrical connection to an external power source. Detector 114 may beadapted to receive a light signal reflected from the pregnant mammaland/or the fetus and convert this light signal into an electronicsignal, which may be communicated to transceiver 107. Some embodimentsof fetal hemoglobin probe 115 may not include a transceiver 107 as maybe the case when, for example, detector 114 is in direct communicationwith, for example, computer 150. Exemplary detectors 114 include, butare not limited to, cameras, traditional photomultiplier tubes (PMTs),silicon PMTs, avalanche photodiodes, and silicon photodiodes. In someembodiments, the detectors will have a relatively low cost (e.g., $50 orbelow), a low voltage requirement (e.g., less than 100 volts), andnon-glass (e.g., plastic) form factor. However, these alternatives donot have the same sensitivity to PMTs. In other embodiments, (e.g.,contactless pulse oximetry) an extremely sensitive camera may bedeployed to receive light reflected by the pregnant mammal's abdomen.

Light source(s) 105 may transmit light at various wavelengths, includingNIR, into the pregnant mammal's abdomen. Typically, the light emitted bylight source(s) 105 will be focused or emitted as a narrow beam so as toreduce spreading of the light upon entry into the pregnant mammal'sabdomen. Light source(s) 105 may be, for example, a LED and/or a LASER.In some embodiments, light source(s) 105 may be an array of two or morelight source(s) 105 as will be discussed below with regard to FIGS.2C-2E. An exemplary light source 105 is one with a relatively small formfactor and high efficiency so as to limit heat emitted by the lightsource 105. In one embodiment, light source 105 is configured to emitlight at 850 nm an example of which is the LED in Dragon Dome Packagethat Emits Light of 850 nm manufactured by OSRAM Opto Semiconductors(model number SFH 4783), which has a length of 7.080 mm and a width of6.080 mm. Another exemplary light source 105 is a LED configured to emitlight of 730 nm, such as the GF CSHPM1.24-3S4S-1 manufactured by OSRAMOpto Semiconductors, which has a height of 1.58 mm and a length of 3.1mm. Exemplary flux ratios for light source(s) include, but are notlimited to a luminous flux/radiant flux of 175-260 mW, a total radiantflux of 300-550 mW and a power rating of 0.6 W-3.5 W.

In some embodiments, one or more light sources 105 may be a fiber opticcable transmitting light produced by another source (e.g., a LASER ortunable light bulb or LED) not resident within fetal hemoglobin probe115. In some instances, the light source(s) 105 may be tunable orotherwise user configurable while, in other instances, one or more ofthe light sources may be configured to emit light within a pre-definedrange of wavelengths. Additionally, or alternatively, one or morefilters (not shown) and/or polarizers may filter/polarize the lightemitted by light source(s) 105 to be of one or more preferredwavelengths. These filters/polarizers may also be tunable or userconfigurable.

In some embodiments, the fetal hemoglobin probe 115 may direct NIR lightof a plurality of wavelengths (e.g., 7, 6, 5, 4, 3, 2) via light sources105. In a preferred embodiment, five different wavelengths are usedwherein a first wavelength is used to measure an oxygen saturation levelof adult oxyhemoglobin, a second wavelength is used to measure an oxygensaturation level of adult de-oxyhemoglobin, a third wavelength is usedto measure an oxygen saturation level of fetal oxyhemoglobin, and afourth wavelength is used to measure an oxygen saturation level of fetalde-oxyhemoglobin. The fifth wavelength may be used to clean up/improvethe signal by assisting in the detection of portions of the reflectedsignal that may be caused and/or distorted by substances other than thepregnant mammal's and/or the fetal hemoglobin. For example, melanin andbilirubin are known to absorb infrared light. Thus, in instances wherethe fetus and/or pregnant mammal has a darker pigment or when either orboth are jaundiced, the associated melanin and/or bilirubin may distortthe readings of the fetal hemoglobin probe 115 which may result inincorrectly calculating the oxygen saturation of the fetal and/orpregnant mammal's hemoglobin. The fifth wavelength may acts to test forthese distortions so that they may be removed from the received signaland accurate oxygen saturation levels may be determined.

In some embodiments, detector 114 may be a sensitive camera adapted tocapture small changes in fetal skin tone caused by changes incardiovascular pressure as the fetus' heart beats. In these embodiments,fetal hemoglobin probe 115 may be in contact with the pregnant mammal'sabdomen, or not, as this embodiment may be used to perform so-calledcontactless pulse oximetry. In these embodiments, light source(s) 105 offetal hemoglobin probe 115 may be adapted to provide light (e.g., in thevisible spectrum, near-infrared, etc.) directed toward the pregnantmammal's abdomen so that the detector 114 is able to receive lightreflected by the pregnant mammal's abdomen and fetus. The reflectedlight captured by detector 114 in this embodiment may be communicated,via transceiver 107, to computer 150 for processing so as to convert theimages to a measurement of fetal hemoglobin oxygen saturation accordingto, for example, one or more of the processes described herein.

In this embodiment, adjustment mechanism 122 may be adapted to, forexample, focus light source(s) 105, change a frequency of light emittedby light source(s) 105, change a distance light source(s) 105 and/ordetector 114 is positioned away from the surface of the pregnantmammal's abdomen, and/or change an incident location of the emittedlight.

Optionally, fetal hemoglobin probe 115 may also include one or morepolarizers (not shown). A polarizer may act to polarize one more of thewavelengths of light prior to emission by fetal hemoglobin probe 115.Polarizing the light and giving it a specific orientation may serve to,for example, assist in the identification of a signal and/or distinguisha desired signal from noise and thereby improve a signal to noise ratio(SNR) of the received signal.

Transceiver 107 may be configured to the electronic signal(corresponding to the reflected light signal detected by detector 114)from detector 114 and communicate the electronic signal to equipment(e.g., receiver 145 and/or computer 150) external to fetal hemoglobinprobe 115 via, for example, a fiber optic cable (in the case of a lightsignal) and/or a wireless or a wired signal (e.g., via an Ethernet portor hard-wired connection in the case of an electrical signal). In someinstances, transceiver 107 may be a solid-state transceiver. In someembodiments, transceiver 107 may be resident in and/or a part ofdetector 114 and may be configured to detect light and/or photonsreflected from the pregnant mammal and fetus and convert the detectedlight/photons into an electrical signal.

FIG. 2C shows another exemplary fetal hemoglobin probe 115B thatincludes power supply 160, light source(s) 105, transceiver 107,detector 114, an adjustment mechanism 122, a temperature probe 165, anda controller 112.

Temperature probe 165 may be any appropriate mechanism for obtaining atemperature measurement for the pregnant mammal. Adjustment mechanism122 may be one or more mechanisms adapted to adjust one or moreproperties of the light emitted by light source(s) 105 and/or adirection/incident angle of the light directed into the abdomen of thepregnant mammal. Exemplary adjustment mechanisms include, but are notlimited to, filters and polarizers that may be used to adjust afrequency/wavelength of the light emitted by light source(s) 105 and/oran orientation for the light. Other exemplary adjustment mechanisms 122include lenses adapted to, for example, focus or spread light directedinto the pregnant mammal's abdomen. In some instances, the lenses mayalso change the angle of incidence for the light directed to thepregnant mammal's abdomen. In some embodiments, adjustment mechanisms122 may also include mechanisms enabled to move a light source 105and/or operate a lens, filter, or polarizer. In some embodiments,adjustment mechanism 122 may include a material that is sensitive toelectricity and may be enabled to become transparent and/or partiallyopaque upon application of electricity. Often times, adjustmentmechanism(s) 122 may receive instructions from controller 112 that maycontrol (wholly or partially) the operation of the adjustment mechanism122.

Optionally, fetal hemoglobin probe 115 may also include one or more oneor more ultrasonic detectors 170. An ultrasonic detector 170 may beemployed in embodiments of fetal hemoglobin probe 115 configured toperform optoacoustic/photoacoustic and/or thermoacoustic imaging by wayof directing a light or radio frequency pulse from light source(s) 105into the pregnant mammal's 305 abdomen. A portion of the incident lightmay be absorbed by the fetus and pregnant mammal and converted intoheat, which leads to transient thermoelastic expansion, which causes anultrasonic emission from the fetus and pregnant mammal. This ultrasonicemission may be detected by ultrasonic detector 170 and analyzed todetermine a level of oxygen saturation for the fetus' and/or pregnantmammal's blood. In some instances, deploying fetal hemoglobin probe 115to perform optoacoustic/photoacoustic and/or thermoacoustic imaging mayrequire use of a laser and/or radio frequency pulse emitter (not shown).

Controller 112 may be adapted to control one or more components (e.g.,adjustment mechanism 122, light source(s) 105, power supply 160,temperature probe 165, detector 114, and/or transceiver 107) of fetalhemoglobin probe 115. In some circumstances, controller 112 may includea processor adapted to receive measurements/information from one morecomponents (e.g., adjustment mechanism 122, light source(s) 105, powersupply 160, temperature probe 165, detector 114, and/or transceiver 107)of fetal hemoglobin probe 115. The processor may be further adapted toprocess the received measurements, make decisions therewith, andcommunicate instructions based on those decisions and/or measurements toone or more components of fetal hemoglobin probe 115. For example,temperature probe 165 may act to measure the body temperature of thepregnant mammal and may provide these measurements to controller 112and/or transceiver. In some embodiments, these measurements may be usedto determine whether the temperature of the pregnant mammal exceeds athreshold measurement, which in some instances, may indicate that lightsource(s) 105 and/or fetal hemoglobin probe 115 are delivering too muchheat/energy to the pregnant mammal. Upon reaching such a determination,controller 112 may provide instructions to light source(s) 105 and/oradjustment mechanism 122 to correct for this. Exemplary instructionsinclude, but are not limited to, directions to redirect incident light,turn off, adjust a frequency, and adjust an intensity of one or more ofthe light source(s) 105.

In some instances, instructions provided by controller 112 may be basedon, for example, feedback from, for example detector 114 and/ortransceiver 107 regarding, for example, the strength/intensity of thereflected signal, the frequency/wavelength of light received in thereflected signal. For example, if controller 112, transceiver 107,and/or detector 114 determines that a received signal reflected from thepregnant mammal's abdomen is of insufficient strength/intensity, thencontroller 112 may provide instructions to adjustment mechanism 112and/or light source(s) 105 to increase the intensity and/orwavelength/frequency of the light incident on the abdomen of thepregnant mammal.

In another example, temperature probe 165 may act to measure the bodytemperature of the pregnant mammal and may provide these measurements tocontroller 112 and/or transceiver. In some embodiments, thesemeasurements may be used to determine whether the temperature of thepregnant mammal exceeds a threshold measurement, which in someinstances, may indicate that light source(s) 105 and/or fetal hemoglobinprobe 115 are delivering too much heat/energy to the pregnant mammal.Upon reaching such a determination, controller 112 may provideinstructions to light source(s) 105 and/or adjustment mechanism 122 tocorrect for this. Exemplary instructions include, but are not limitedto, directions to redirect incident light, turn off, adjust a frequency,and/or adjust an intensity of one or more of the light source(s) 105.

In some instances, light source(s) 105 may be tunable, or otherwise userconfigurable, by, for example, a physician or clinician assisting thepregnant mammal during the delivery process. For example, a light source105 may be configured to emit light in multiple frequencies/wavelengthsand/or intensities and the light source 105 may be tuned via, forexample, direct physical manipulation of the light source 105 (e.g., viaa button on knob), or the entering of an instruction regarding thedesired frequency/wavelength and/or intensity into, for example,computer 150 and/or controller 112.

Tuning the frequency/wavelength and/or intensity of light emitted by oneor more light source(s) 105 may be helpful in achieving a return signalof sufficient strength or clarity in a variety of circumstances (e.g.,fetus position, fetus size, the amount of melanin in the skin of thepregnant mammal and/or fetus, the size and/or shape of the pregnantmammal, etc.). For example, light of a relatively higher intensity maybe desired when the pregnant mammal has a relatively high body massindex (BMI) or body fat positioned in such a way as to inhibit thestrength of a signal reflected from the fetus (i.e., return signal). Inanother example, a fetus may be positioned against the internal organsof the pregnant mammal (i.e., away from the skin of the belly), andlight of relatively higher intensity and/or different wavelength may bedesired so that the light reaches the fetus with a sufficiently strongsignal so that a return signal may be detected by, for example, detector114.

When fetal hemoglobin probe 115 includes more than one light source 105,the light sources 105 may be arranged in an array adapted to maximizethe strength of the returned signal such as array 170 as discussed belowwith regard to FIGS. 2D and 2E. Array 170 may include any appropriatenumber of light sources 105. In some instances, array 170 may include afirst row of a first type of light source 105A, 105B, through 105N and asecond row of a second type of light source 105 AA, 105AB, through105AN. The different types of light sources may be configured to, forexample, emit light of a particular frequency/wavelength and/orintensity. For example, light sources 105 A, 105B, through 105N may beconfigured to emit light with wavelengths in the red spectrum and lightsources 105 AA, 105AB, through 105AN may be configured to emit lightwith wavelengths in the infrared or near-infrared spectrum. Althougharray 170 to have two rows, it will be appreciated that any number ofrows (e.g., 3, 4, 5, 6, 7, 8, and so on) may be included in array 170.

Embodiments of fetal hemoglobin probe 115 with a relatively large length(e.g., 10 cm-40 cm) may have arrays 170 with rows of multiple lightsources long fetal hemoglobin probe 115 that include, for example, 10,15, 20, 25, 30, 35, 40, 45, or 50 light sources 105 each. A fetalhemoglobin probe 115 may also include more than one detector 114, asshown in FIG. 2E, which includes a first detector 114A and a seconddetector 114B. In some embodiments, first detector 114A may be the sameas second detector 114B and, in other embodiments, they may bedifferent. For example, first detector 114A may be sensitive to a firstrange of frequencies for reflected light and second detector 114B may besensitive to a second range of frequencies for reflected light.Additionally, or alternatively, first detector 114A may be of adifferent size than second detector 114B. Any of the fetal hemoglobinprobes 115 disclosed herein may include multiple detectors adapted to,for example, detect light reflected for one or more the light source(s)105 included in array 170.

Although shown as a separate component in FIGS. 2C-2E, it will beappreciated by those of skill in the art that adjustment mechanism 122may be partially and/or wholly positioned within and/or adjacent to oneor more light sources 105.

Components of system 100 may be applied to a pregnant mammal in anyacceptable manner. For example, NIRS adult hemoglobin probe 125 may beplaced on the second finger of the pregnant mammal 305, pulse oximetryprobe 130 may be placed on the thumb of the pregnant mammal 305, andDoppler and/or ultrasound probe 135 may be placed on the abdomen of theon the pregnant mammal.

In some implementations, uterine contraction measurement device 140 mayalso be on placed on the abdomen of the pregnant mammal. In otherimplementations, uterine contraction measurement device 140 may beembodied in the fetal hemoglobin device 115. In some cases, uterinecontraction measurement device 140 may be a pressure sensor configuredto detect the changes in pressure of the uterine muscle in units ofpressure (mmHg and/or kPa).

In some embodiments, one or more light source(s) 105 and detector(s) 114may act as an optoelectronic muscle contraction sensor without the needfor a separate uterine contraction measurement device 140. In theseembodiments, the light reflected from the pregnant mammal's uterus mightchange in nature when the uterus is in a relaxed state (more scattering)as opposed to a contracted state (less scattering). These changes in therate of scattering of the light may be detected by one or moredetector(s) 114 and processed by, for example, computer 150 to determinechanges in the state of the uterine muscle. In some embodiments, one ormore light source(s) 105 may direct light of a particularfrequency/wavelength so that measurements of uterine contractions have adedicated beam/frequency of light.

Preferably, the fetal hemoglobin probe 115 is placed at, or near, thebikini/supra-pubic region of the pregnant mammal 305. This area istypically right above the pubic hairline. This position is advantageousin the later stages of pregnancy, for example, after 9 months or 36weeks of gestational development because the fetus's head will engageinto the cervical birth canal and will, therefore, be in a fairlypredictable location within the abdomen of the pregnant mammal.Additionally, when the head of the fetus is positioned within thecervical birth canal, the distance between pregnant mammal and fetus isminimal and therefore NIR light passing through the abdomen of thepregnant mammal is more likely to come into contact with the fetus andbe reflected back to the fetal hemoglobin probe 115.

FIGS. 3A, 3B, and 3C provide illustrations of how light from fetalhemoglobin probe 115 may be directed into a pregnant mammal's 305abdomen and reflected light may be detected by one or more detectors 114of fetal hemoglobin probe 115. More specifically, FIG. 3A provides across sectional view of fetal hemoglobin probe 115 and of the pregnantmammal 305 as divided along a midline extending through the center ofpregnant mammal 305 when she is viewed from the front (i.e., through thecenter of the face, between the breasts, etc.). FIG. 3A depicts anapproximation of a fetus 310 that is surrounded by amniotic fluid andother tissue 315 present in a uterus 320 of the pregnant mammal 305.fetal hemoglobin probe 115 is show in FIG. 2C to be positioned on thelower abdomen of the pregnant mammal 305 at, or near, thebikini/supra-pubic region of the pregnant mammal 305.

As shown in FIG. 3A, a beam of light 325 (also referred to herein as an“incident beam”) emitted from one or more light source(s) 105 isincident on pregnant mammal's 305 abdomen and is directed toward fetus310. Beam of light 325 may be of any wavelength/frequency or combinationof wavelengths/frequencies. In one embodiment, incident beam 325 mayinclude light that is in the red spectrum and the near infraredspectrum.

In some embodiments, incident beam 325 may include two or more beams oflight that may be emitted from, for example a single light source 105(that emits two beams of light of the same frequency and/or a beam oflight of two different frequencies) or two different light sources 105(e.g., one frequency per light source). When two or more beams areincluded in incident beam 325, they may, on occasion be directed inslightly different directions so as to, for example, accommodatedifferences in the frequency of the light of the beam, a condition ofthe pregnant mammal 305 (e.g., skin pigmentation, body mass index, etc.)and/or a condition of the fetus (e.g., size, position, location withinthe uterus, skin pigmentation, etc.).

A portion of incident beam 325 may reflect from the fetus 310, amnioticfluid and other tissue 315, and uterus 320 as a reflected beam 330 andmay be received by one or more detectors 114 provided by fetalhemoglobin probe 115. Although reflected beam 330 is shown as one beam,it may be any number of beams or individual photons. It is expected thatnot all of the light of incident beam 325 will be included in reflectedbeam 330 as some of the light of incident beam 325 may belost/undetected due to, for example, scattering and/or absorption.

FIG. 3B provides an image of fetal hemoglobin probe 115 with anadjustment device 335 positioned between the skin of the pregnantmammal's 305 abdomen and a portion of fetal hemoglobin probe 115. In theembodiment of FIG. 3B, adjustment device 335 is triangular in shape andacts as a wedge to change an orientation/position of fetal hemoglobinprobe 115 (and the corresponding orientation/position of light source(s)105 and/or detector(s) 114) relative to the pregnant mammal's abdomen.In some cases, adjustment device 335 may change the angle of incidencefor incident beam 325 and/or an orientation of one or more detectors114. In some embodiments, adjustment device 335 may be transparent so asto allow for the passage of light into, and out of, the pregnantmammal's 305 abdomen. In other embodiments, adjustment device 335 may besemi-transparent or opaque so as to, for example, change a frequency ofthe incident beam 325 and/or reflected beam 330.

Adjustment device 335 may be configured to adjust for physiologicalconditions of the pregnant mammal's 305 abdomen that make it difficultto receive a reflected beam of sufficient strength. For example, for apregnant mammal 305 with a high fat content around her abdomen, applyingthe fetal hemoglobin probe 115 directly to the pregnant mammal's 305skin may not direct the incident beam 325 in the proper direction and/orenable detection of the reflected beam 330. Additionally, oralternatively, adjustment device 335 may be configured to adjust forphysiological conditions of the fetus 310 including the size and/orplacement of the fetus 310 within the uterus 320. For example,adjustment device 335 may be deployed so as to direct incident beam 325toward the head of fetus 310.

In some embodiments, two or more adjustment mechanisms 335 may be used.An adjustment device 335 may be of any appropriate shape and/orconfiguration including, but not limited to, a triangle, circle, orrectangle and may be configured to adjust the positioning or operationof some, or all, of the components of fetal hemoglobin probe 115. Insome instances, adjustment device 335 may be designed to improve thecomfort of the pregnant mammal 305 while wearing fetal hemoglobin probe115 and, to that end, may be configured to include soft and/or flexiblematerial (e.g., foam) designed to adapt to a contour of the pregnantmammal's abdomen. In these instances, adjustment device 335 would bedesigned to engage with fetal hemoglobin probe 115 in a manner that doesnot obscure one or more components thereof.

In another embodiment, adjustment device 335 may include optics,filters, or other mechanical and/or electrical components configured toadjust one or more features of incident beam 325 and/or reflected beam330. In some instances, one or more operations of adjustment device 335may be performed upon receipt of instructions from, for example, acomponent of fetal hemoglobin probe 115 and/or computer 150.

FIG. 3C provides a front view of pregnant mammal's 305 abdomen withfetal hemoglobin probe 115 affixed thereto. The perspective is somewhatadjusted for FIG. 3C so that incident beam 325 and reflected beam 330may be seen. In reality, both incident beam 325 and reflected beam 330are directed into/reflected from the pregnant mammal's 305 abdomen alongthe —Z-axis.

FIG. 3D provides a front cross section view of pregnant mammal's 305abdomen with fetal hemoglobin probe 115 and Doppler/ultrasound probe 135coincident therewith. As shown in FIG. 3D, Doppler/ultrasound probe 135transmits a beam into pregnant mammal's 305 abdomen towards fetus 310and receives a reflected signal. Doppler/ultrasound probe 135 is thenuses this reflected signal to determine a fetal heart beat signal and/ordetermine a number of fetal heart beats per minute. and

The fetal hemoglobin probe 115 of FIG. 3D has two light sources, a firstof which, 105A, emits a light beam 325A of a first wavelength (λ₁)(noted on the figure as 105A, λ₁ and 325A, λ₁, respectively) and asecond of which, 105B, emits a light beam 325B of a second wavelength(λ₂) (noted on the figure as 105B, λ₂ and 325B, λ₂, respectively). Aportion of incident beams 325A and 325B is reflected by the pregnantmammal 305 and fetus 310 and received by detector 114 as reflected beam330A and 330B, respectively ((noted on the figure as 330A, λ₁ and 330B,λ₂, respectively).

FIG. 4A illustrates an exemplary process 400 for performing fetaloximetry and/or fetal pulse oximetry trans-abdominally and/or in-uteroto determine fetal hemoglobin oxygen saturation level. Process 400 maybe performed by, for example, system 100 and/or a component thereof.

Initially, a light beam, such as incident beam 325, is directed into theabdomen of a pregnant mammal, such as pregnant mammal 305 (step 405) by,for example, one or more light sources such as light source(s) 105provided by one or more of the fetal hemoglobin mammal' pregnantmammal's abdomen may be directed toward the pregnant mammal's fetus,such as fetus 310 as shown in FIGS. 3A and 3B discussed above.

The light beam directed into the pregnant mammal's abdomen may includeany number of light beams and/or frequencies/wavelengths of light asdescribed above with regard to incident beam 325. In some instances, thelight beam of step 405 may be a plurality of light beams emitted from aplurality of light sources positioned at a plurality of differentlocations along the abdomen of the pregnant mammal as shown in, forexample, FIGS. 2D and 2E. Additionally, or alternatively, the light beamof step 405 may include a plurality of wavelengths/frequencies emittedby a single of light source that may, for example, include multipleLEDs.

In some embodiments, the light beam of step 405 may include light offirst and second wavelengths with a first of the wavelength being in thered portion of the electromagnetic spectrum (i.e., 620-750 nm) and asecond of wavelengths in the near-infrared (NIR) portion of theelectromagnetic spectrum (e.g., 750 nm-2,500 nm). Use of thesewavelengths is preferred, but not required, because light of wavelengthsin the red and near-infrared spectrum are known to travel through,and/or be reflected by, skin and body tissue. In some embodiments, lightof, for example, a third, fourth, fifth, or more different wavelengthsmay be directed toward the abdomen of the pregnant mammal. In somecircumstances, use of more than two wavelengths of light may be usefulto enhance reflected signal strength and/or clarity in variouscircumstances including, but not limited to, distance of the fetus fromthe external skin, or uterine wall, of the pregnant mammal (i.e., depthof the fetus), level of melanin/pigment in the skin of the pregnantmammal and/or fetus, strength of fetal pulse signal, how much the fetusmoves within the placenta and/or uterus of the pregnant mammal, and soon.

In some embodiments, an intensity of the light directed into thepregnant mammal at step 405 may be varied and/or different for differentwavelengths of light. For example, the intensity of red light directedinto the pregnant mammal's abdomen may be greater than the intensity ofthe near-infrared light due to the transmission/reflection properties ofred light verses near infrared light (i.e., near-infrared light is knownto reflect more light when shown into body tissue than red light).However, it is expected that an intensity of the light beam of step 405will be safe for both the pregnant mammal and her fetus (e.g., not causeburns to the pregnant mammal's skin and/or damage to fetal tissue (e.g.,eyes)).

In step 410, light (e.g., waves and/or photons) reflected by the abdomenof the pregnant mammal (and the fetus) may be received by one or moredetectors (e.g., photo-sensor, photo detectors or photodiodes), such asdetector 115 and/or transceiver 107 and converted (step 415) into anelectronic signal that represents the reflected light (this signal maybe referred to herein as a “reflected electronic signal” by thephoto-sensor/photodiode/photo detector. In some instances, the lightdirected into the abdomen of the pregnant mammal, may travel a distanceof, for example, 3-5 cm to contact the fetus and another 3-5 cm oncereflected from the fetus to be detected by the detector. Thus, the totaltravel distance for the incident and reflected beam may be as high as 8or 10 cm. When traveling this distance, a substantial amount ofscattering and other interference in the detection of a reflected signalmay occur and it is possible that only a small fraction (e.g., 0.5-5%)of the light incident on the abdomen of the pregnant mammal will bereflected by the fetus and received by detector.

Optionally, in step 420, it may be determined whether the electronicreflected signal is of sufficient strength to detect, for example, thepulse and/or fetal oxygen saturation of the fetus. Exemplary signalstrengths that are sufficient are in the range of 30-500 dB with asignal-to-noise (SNR) ratio of 1-8, with a preferred SNR ofapproximately 3-4.5.

When the signal isn't of sufficient strength, the light source(s) and/ordetector(s) may be adjusted automatically (i.e., without operatorintervention) and/or provision of an indication that an adjustment ofthe light source(s) and/or detector(s) may be desired or needed to anoperator (e.g., doctor or nurse) may be facilitated (step 425).Exemplary indications provided in step 425 include, but are not limitedto, an alarm, a message (e.g., written or audio), and a recommendation.Exemplary automatic adjustments include, but are not limited to,adjusting a lens positioned between the pregnant mammal's abdomen andthe light source(s) and/or detector(s) so as to focus the light emittedby the light source(s) and/or received by the detector(s), adjusting anamount of power delivered to the light source(s) and/or detector(s),adjusting an intensity and/or frequency of the light emitted by one ormore of the light source(s) and so on. In some embodiments, activationof additional light sources to direct light into the pregnant mammal'sabdomen may be responsive to a determination that the electronicreflected signal is not of sufficient strength.

In some instances, the adjustment(s) of step 425 may be performed and/orfacilitated by one or more adjustment mechanisms, such as adjustmentmechanisms 122 and/or controllers, such as controller 112. Onceadjusted, the light beam may again be directed into the pregnantmammal's abdomen (i.e., step 405 may be repeated) and steps 410-420 maybe repeated. When the electronic reflected signal is of sufficientstrength, or when steps 420 and 425 are not performed, process 400 mayadvance to step 430.

In step 430, the electronic reflected signal may be processed to isolatea portion of the reflected electronic signal reflected from the fetus(as opposed to the pregnant mammal or noise). For ease of discussion,the portion of the reflected electronic signal reflected from the fetusmay be referred to herein as the fetal reflected electronic signal.Examples of how step 430 may be executed are discussed below with regardFIGS. 5A-5D. Following step 430, the fetal reflected electronic signalmay be analyzed to determine the oxygen saturation level of hemoglobincontained in the fetus' blood via, for example, oximetry and/or pulseoximetry techniques (step 440). Typical values for the oxygen saturationof fetal blood fall within the range of 30-70%. An exemplary method ofdetermining fetal hemoglobin saturation level uses a version of theBeer-Lambert law modified to account for the scattering effect of thereflected light as it is scattered by tissues in the body as describedby Zourabian, Anna, et al., Trans-abdominal Monitoring of Fetal ArterialBlood Oxygenation Using Pulse Oximetry, Journal of Biomedical Optics,5(4), pp. 391-405 (October 2000), which is incorporated by referenceherein. Further details regarding execution of step 435 is providedbelow with regard to FIGS. 6A-6H.

Then, in step 440, provision of an indication of fetal oxygen level toan operator may be facilitated. Exemplary operators include, but are notlimited to, doctors, nurses, and other caregivers. Exemplary indicatorsinclude a waveform shown on a display device (e.g., computer monitor), anumerical value provided via a display device and/or message (e.g., SMStext message), such as a fetal hemoglobin oxygen saturation level.Facilitating provision of the indication of step 465 may includeproviding the indication to a computer, such as computer 150 and/or adisplay device such as display device 155. An example of such a displayof fetal hemoglobin oxygen saturation level is provided by FIGS. 8A and8B and is discussed below.

One method of processing the signal to isolate the portion of thereflected electronic signal reflected from the fetus from the totalreflected electronic signal is to multiply the total reflectedelectronic signal by signal that provides the fetal heart (i.e., performstep 430) beat as may be provided by, for example, a Doppler and/orultrasound probe such as Doppler/ultrasound probe 135. The resultantsignal (i.e., the signal that is the product of multiplying the totalreflected electronic signal and the fetal heartbeat signal) mayapproximate the portion of the total reflected electronic signalreflected by the fetus. To improve this approximation, the signalreading may be averaged over a number of cycles to provide a moreaccurate approximation of the portion of the total reflected electronicsignal reflected by the fetus. An example of this process is provided byFIGS. 5A-5D, of which FIG. 5A provides a graph 500 of total reflectedelectronic signal intensity vs. time and represents light reflected bythe abdomen of the pregnant mammal detected in step 410. FIG. 5Bprovides a graph 501 of a Doppler signal vs. time. This signal andrepresents light reflected by the abdomen of the pregnant mammaldetected in step 410. The Doppler signal represents the fetus'heartbeat. This signal may be received from, for example,Doppler/ultrasound probe 135. FIG. 5C provides a graph 502 that showsthe product of multiplying the total reflected electronic signalintensity (from FIG. 2A) and the Doppler signal (from FIG. 2B) togetherwhile synchronizing over time so that a signal intensity of the totalreflected electronic signal at a particular moment in time is multipliedby the Doppler signal intensity at that same particular moment in time.The resultant signal shown in FIG. 5C approximates the portion of thetotal reflected electronic signal reflected from the fetus. This signalmay then be analyzed to determine fetal oxygen saturation levels using,for example, oximetry or pulse oximetry techniques.

In some embodiments, the accuracy of the approximated portion of thetotal reflected electronic signal reflected from the fetus may beimproved by averaging a number of signal intensities over a period oftime (e.g., a number of periods) as shown in FIG. 5D, which provides agraph 503 of the total reflected electronic signal intensity, the fetalheartbeat/Doppler signal and the result of multiplying total reflectedelectronic signal intensity and Doppler signal synchronized over time(referred to on graph 503 as “fetal reflected signal.”

Another method of processing the electronic reflected signal to isolatethe portion of the reflected electronic signal reflected from the fetusfrom the total reflected electronic signal is to multiply the totalreflected electronic signal by signal that provides the fetal heart(i.e., perform step 430) is provided by FIG. 4B, which shows sub-process401.

In step 445 of sub-process 401, a heartbeat signal for the pregnantmammal is received from, for example, a pulse oximetry probe like pulseoximetry probe 130 and/or an adult hemoglobin probe like NIRS adulthemoglobin probe 125. Next, the received pregnant mammal's heartbeatsignal may be synchronized in the time domain with the electronicreflected signal (step 450). Then a correlation between the pregnantmammal's heartbeat and changes in the electronic reflected signal may beestablished so as to determine a portion of the electronic reflectedsignal that is reflected by the pregnant mammal (step 455). In step 460,the portion of the portion of the electronic reflected signal that isreflected by the pregnant mammal is then subtracted from the electronicreflected signal with the portion of the electronic reflected signalreflected by the fetus being thereby isolated.

Another method of processing the signal to isolate the portion of thereflected electronic signal reflected from the fetus from the totalreflected electronic signal is to multiply the total reflectedelectronic signal by signal that provides the fetal heart (i.e., performstep 430) is provided by FIG. 4C, which shows sub-process 402.

In step 465 of sub-process 402, a heartbeat signal for the fetus may bereceived from, for example, an ultrasound device and/or a Dopplerdevice, such as Doppler/ultrasound probe 135. Next, the received fetus'heartbeat signal may be synchronized in the time domain with theelectronic reflected signal (step 470). Then, portions of the electronicreflected signal that correspond in the time domain with the individualheartbeats may be examined (step 475). In this way, the entireelectronic reflected signal does not have to be processed/analyzed; onlythe portions of the electronic reflected signal where a fetal heartbeat,or pulse, occur are examined. This saves processing time and resourcesbecause the entire signal does not have to be processed.

In some embodiments, the processing of step 430 and/or analysis of step435 may include processing the reflected electronic signal in order toascertain a signal that corresponds to the absorption/reflection of NIRlight by oxygenated hemoglobin and deoxygenated hemoglobin of the fetus.Using this information, a level (or percentage) of fetal hemoglobinoxygen saturation (step 435) may be determined.

Because fetal hemoglobin is structurally different from adult hemoglobinit absorbs light differently and the signal reflected from the fetalhemoglobin at various wavelengths will be of a different magnitude whencompared to the magnitude of the signal at those same wavelengthsreflected by the pregnant woman. In this way, measuring a quantity oflight reflected from the hemoglobin of the pregnant woman and fetus atvarious wavelengths will provide an indication of the amount of light ofa particular wavelength that is absorbed by the fetal hemoglobin as wellas the pregnant woman's hemoglobin. Looking at the ratios of lightreflected at various wavelengths will provide a benchmark thatcorrelates to a specific fetal blood oxygen level. In some instances,the variations in wavelength absorption of the fetal hemoglobin whencompared to the pregnant woman's hemoglobin may not be sufficient toprovide an adequately strong or clear signal indicating fetal hemoglobinoxygen saturation levels for clinical and/or diagnostic purposes.Therefore, one or more signal processing techniques may be applied tothe signal received by the fetal hemoglobin probe 115 to determine fetalhemoglobin oxygen saturation as will be discussed in detail below.

In an exemplary signal processing technique, a signal received from thepregnant woman's pulse oximetry probe (e.g., pulse oximetry probe 130)may be used to determine the oxygen saturation level of the pregnantwoman's arterial blood, which corresponds to an oxygenated state ofpregnant woman's hemoglobin. The pulse oximetry probe is used to makethis determination because the depth of a human finger is 1-2 cm, ameasurable amount of light can pass through the fingertip and there isno interference from fetal blood flow or circulating fetal hemoglobin atthe pregnant woman's fingertip position. Hence, a reading from pulseoximetry probe 130 will directly correspond to how much light isabsorbed and/or reflected at various wavelengths by the pregnant woman'sadult hemoglobin. This information may be used to understand how thelight is interacting with pregnant woman's hemoglobin near the fetus andthis information may be subtracted from the signal received by the fetalhemoglobin probe 115 to determine how much light is absorbed and/orreflected at various wavelengths by the fetus' hemoglobin.

Additionally, or alternatively, the signal received by the fetalhemoglobin probe 115 may be processed using a heart rate of the fetusand/or pregnant woman. The timing of the pregnant woman's heartbeatcorrelates to the timing for various levels of blood oxygen saturationfor the pregnant woman. This correlation may be used to detect a signalcorresponding the level of blood oxygen saturation for the pregnantwoman within the signal received by the fetal hemoglobin probe 115. Thefetal oxygen saturation level may then be determined by subtracting, orotherwise filtering, the detected signal corresponding the level ofblood oxygen saturation for the pregnant woman from signal received bythe fetal hemoglobin probe 115.

Additionally, or alternatively, the fetal heartbeat correlates to thetiming for various levels of blood oxygen saturation for the fetus. Thiscorrelation may then be used to detect a signal corresponding the levelof blood oxygen saturation for the fetus within the signal received bythe fetal hemoglobin probe 115. For example, Doppler/ultrasound probe135 and/or an ultrasound device may indicate that the fetus' heart rateis in the range of 120-160 beats per minute and this fetal heart ratemay be used to gate and/or correlate a NIR signal from the fetus.

In the rare circumstance when the fetal heart rate and maternal heartrate are similar (fetal bradycardia and maternal tachycardia) the twoheartbeats may be distinguished from one another using the known factthat there is a slight pause in the heart rate during respiration. So,by monitoring the heart rate signal (via, e.g., pulse oximetry probe130), one may observe that the pregnant woman's the heart rate slowsdown for a moment when she takes in a deep breath. This slowing willonly be present in the signal providing the pregnant woman's heart ratebecause fetuses do not breathe while in utero. In this way, the twoheart rates may be distinguished from one another.

In some embodiments, a signal from NIRS adult hemoglobin probe 125 maybe processed to determine a ratio of adult oxyhemoglobin to adultde-oxyhemoglobin. This ratio may then be used to subtract readings fromthe pregnant woman's blood flow so that a signal from the fetus's bloodflow may be isolated and analyzed to, for example, determine a level offetal hemoglobin oxygen saturation.

In other embodiments, processing the signals received by the fetalhemoglobin probe 115 may include oscillating between time domain andfrequency domain analysis. This oscillation may allow identificationsignals that have a cyclical (periodic) component as opposed to signalsthat are random or non-periodic (acyclic/aperiodic). Random ornon-periodic signals are more likely to be noise and examining thereceived signal for random or non-periodic signals will assist indetermining a noise level of the signal as well as portions of thesignal that may be filtered or otherwise removed therefrom.

In some embodiments, process 400 may include the establishment of a setof correlations between the intensity of light reflected/absorbed atcertain wavelengths by fetal oxyhemoglobin and de-oxyhemoglobin and theoxygen saturation levels of the fetal oxyhemoglobin andde-oxyhemoglobin. This set of correlations may be performed prior toexecuting process 400 for a particular pregnant mammal during the fetallabor and delivery process and may be stored in, for example, computer150. An exemplary correlation may be a reflection of light of wavelengthA with an intensity X and a reflection of light of wavelength B with anintensity 0.8× to an fetal oxygen saturation level of 50% of fetalhemoglobin being bound to oxygen. Another exemplary correlation may be areflection of light of wavelength A with an intensity X and a reflectionof light of wavelength B with an intensity 0.5× to an fetal oxygensaturation level of 25% of fetal hemoglobin being bound to oxygen.

(noted on the figure as 105A, λ₁ and 325A, λ₁, respectively) and asecond of which, 105B, emits a light beam 325B of a second wavelength(λ₂) (noted on the figure as 105B, λ₂ and 325B, λ₂, respectively). Aportion of incident beams 325A and 325B is reflected by the pregnantmammal 305 and fetus 310 and received by detector 114 as reflected beam330A and 330B, respectively ((noted on the figure as 330A, λ₁ and 330B,λ₂,

FIGS. 6A-6H provide information in the form of graphs regarding anexample of how reflected electronic signal is analyzed to determinefetal hemoglobin oxygen saturation level. At times, fetal hemoglobinoxygen saturation level may also be referred to herein as fetal arterialoxygen saturation level, which may be abbreviated to (% SaO2). Morespecifically, FIG. 6A provides a graph 601 of a Doppler signal vs. time.The Doppler signal corresponds to a fetal heart beat signal. The Dopplersignal of FIG. 6A is similar to the Doppler signal of FIG. 5B.

FIG. 6B provides a graph 602 of reflected electronic signal intensityfor λ₁ vs. time. This graph may correspond to reflected signal 330A, λ₁.Any of the processes discussed above may be used to isolate the portionof the signal reflected by the fetus from the reflected electronicsignal intensity for λ₁. In the example provided, the total reflectedelectronic signal intensity for λ₁ and the fetal Doppler signal aremultiplied together while synchronizing over time to provide the productof multiplying the total reflected electronic signal intensity for λ₁and the Doppler signal together while synchronizing over time as shownin graph 603 of FIG. 6C.

FIG. 6D provides a graph 604 that shows the product of multiplying thetotal reflected electronic signal intensity for λ₁ and the fetal Dopplersignal together while synchronizing over time averaged over severalperiods. This graph (or the data used to generate the graph) is analyzedto determine an intensity of a systolic value for the first wavelengthλ₁ 610, which corresponds to the peak of the curve (i.e., highest value)and an intensity of a diastolic value for the first wavelength λ₁ 615,which corresponds to the trough of the curve (i.e., lowest//smallestvalue).

FIG. 6E provides a graph 605 of reflected electronic signal intensityfor λ₂ vs. time. Any of the processes discussed above may be used toisolate the portion of the signal reflected by the fetus from thereflected electronic signal intensity for λ₂. In the example provided,the total reflected electronic signal intensity for λ₂ and the fetalDoppler signal are multiplied together while synchronizing over time toprovide the product of multiplying the total reflected electronic signalintensity for λ₂ and the Doppler signal together while synchronizingover time as shown in graph 606 of FIG. 6F.

FIG. 6G provides a graph 607 that shows the product of multiplying thetotal reflected electronic signal intensity for λ₂ and the fetal Dopplersignal together while synchronizing over time averaged over severalperiods. This graph (or the data used to generate the graph) is analyzedto determine an intensity of a systolic value for the second wavelengthλ₂ 620, which corresponds to the peak of the curve (i.e., highest value)and an intensity of a diastolic value for the second wavelength λ₂ 625,which corresponds to the trough of the curve (i.e., lowest/smallestvalue).

A modulation ratio (R) between the reflected intensity of twowavelengths of light may be calculated as follows:

$\begin{matrix}{R = {{\log\left( \frac{T_{{sys}\lambda 1}}{T_{{dias}{\lambda 1}}} \right)}/{\log\left( \frac{T_{{sys}{\lambda 2}}}{T_{{dias}{\lambda 2}}} \right)}}} & {{Equation}1}\end{matrix}$

where:T_(sysλ1) is the intensity of the systolic value for the firstwavelength (λ₁);T_(diasλ1) is the intensity of the diastolic value for the firstwavelength (λ₁);T_(sysλ2) is the intensity of the systolic value for the secondwavelength (λ₂); andT_(diasλ2) is the intensity of the diastolic value for the secondwavelength (λ₂).

The modulation ratio, R, may then be used to determine a level ofarterial oxygen saturation value (% SaO2) in one of at least twofashions. When a relationship between a modulation ratio, R, for a pairof wavelengths (i.e., λ₁ and λ₂) and arterial oxygen saturation is known(from, for example, experimentally determined values), then the value ofR may be used to look up a corresponding arterial oxygen saturationlevel. FIG. 6H ¹ provides an exemplary graph that plots a knownrelationship between values for R (when λ₁ is in the red spectrum and λ₂is in the infrared spectrum) with arterial oxygen saturation values. ¹Source of FIG. 6H: Paul D. et al., Wavelength Selection forLow-Saturation Pulse Oximetry, IEEE Transactions on BiomedicalEngineering, Vol. 44, No. 3, March 1997, p. 149.

Following through with the above example (with the appropriate referencenumbers for intensity values inserted from graphs 604 and 607), wouldyield the following calculation for equation 1:

$R = {{\log\left( \frac{610}{615} \right)}/{\log\left( \frac{620}{625} \right)}}$

The ratio, R, calculated from this equation may then be used to find acorresponding arterial oxygen saturation level for the fetus (i.e.,fetal hemoglobin oxygen saturation level).

Fetal oxygen saturation level may also be calculated using the followingequation (Equation 2):

$\begin{matrix}{S = {\frac{{\epsilon_{Hb}^{\lambda_{2}}{R\left( {B^{\lambda_{2}}/B^{\lambda_{1}}} \right)}} - \epsilon_{Hb}^{\lambda_{1}}}{\left( {\epsilon_{HbO}^{\lambda_{1}} - \epsilon_{Hb}^{\lambda_{1}}} \right) - {{R\left( {B^{\lambda_{2}}/B^{\lambda_{1}}} \right)}\left( {\epsilon_{HbO}^{\lambda_{2}} - \epsilon_{Hb}^{\lambda_{2}}} \right)}}.}} & {{Equation}2}\end{matrix}$

where:S is the hemoglobin oxygen saturation,R is the modulation ratio calculated using equation 1;ε_(Hb) is the molar extinction coefficient for deoxygenated hemoglobin;ε_(HbO) is the molar extinction coefficient for oxygenated hemoglobin;andB is a factor the can be estimated by solving the photon diffusionequation for the appropriate measurement geometry via the followingexpression (Equation 3):

$\begin{matrix}{B = {\frac{1}{2}\left( \frac{3\mu_{s}^{\prime}}{\mu_{a}^{initial}} \right)^{1/2}{\left( {1 - \frac{1}{1 + {L\left( {3\mu_{s}^{\prime{initial}}\mu_{a}^{initial}} \right)}^{1/2}}} \right).}}} & {{Equation}3}\end{matrix}$

where:L is the length;μ_(s) is the scattering coefficient;μ_(a) is the absorption coefficient;μ_(s′) is the transport scattering coefficient, which is provided by thefollowing expression (Equation 4):

μ′_(s)=μ_(s)(1−g)  Equation 4

where:g is the anisotropy factor of scattering equal to the average cosine ofthe sing phase scattering function.

Further details regarding the calculations using equations 1, 2, 3, and4 as well as how to determine fetal hemoglobin oxygen saturation levelsare provided by Mannheimer, Paul D. et al., Wavelength Selection forLow-Saturation Pulse Oximetry, IEEE Transactions on BiomedicalEngineering, Vol. 44, No. 3, March 1997, pp. 148-158 and Zourabian,Anna, et al., Trans-abdominal Monitoring of Fetal Arterial BloodOxygenation Using Pulse Oximetry, Journal of Biomedical Optics, 5(4),pp. 391-405 (October 2000), both of which are incorporated by referenceherein.

FIG. 7A provides a table 700 of various hemoglobin measurements as afunction of light wavelength shone into the blood of an adult donor andfetal blood obtained by puncture of the umbilical cord immediately afterdelivery². The values in columns 2-8 of the table are measured inmillimolar absorptivities (L*mmol⁻¹*cm⁻¹). More specifically, the firstcolumn of table 700 provides a list of wavelengths measured innanometers (nm) ranging from 450 nm to 1000 nm, the second column oftable 700 provides a fetal hemoglobin (HbF) measurement in adeoxyhemoglobin state (Hb), the third column of table 700 provides anadult hemoglobin (HbA) measurement in a deoxyhemoglobin state (Hb), thefourth column of table 700 provides a fetal hemoglobin measurement in anoxyhemoglobin state (HbO2), the fifth column of table 700 provides anadult hemoglobin measurement in an oxyhemoglobin state (HbO2), the sixthcolumn of table 700 provides a value representing a difference betweenthe fetal hemoglobin measurement deoxyhemoglobin state and the fetalhemoglobin measurement in an oxyhemoglobin state (Hb−HbO2), the seventhcolumn of table 700 provides a value representing a difference betweenthe adult hemoglobin measurement in a deoxyhemoglobin state and theadult hemoglobin measurement in an oxyhemoglobin state (Hb−HbO2), andthe eighth column of table 700 provides a ratio of the fetal(Hb−HbO2)/HbO2. The data from table 700 is used to make the graphsdepicted in FIGS. 7B and 7C. ² Experimental results are provided byZijistra, W. G., et al. Absorption Spectra of Human Fetal and AdultOxyhemoglobin, De-Oxyhemoglobin, Carboxyhemoglobin, and Methemoglobin,Clin. Chem. Vol. 39/9, pp. 1633-1638 (1991).

FIG. 7B depicts a graph 701 that shows difference in absorptivitiesbetween oxygenated (oxy-) and deoxygenated (deoxy-) state of fetal andthe pregnant woman's hemoglobin in visible wavelengths of light from 450nm to 700 nm wherein the green dashed line represents the difference inabsorptivities between oxy- and deoxy-state of fetal hemoglobin as afunction of wavelength and the red dashed line represents the differencein absorptivities between oxy- and deoxy-state of fetal hemoglobin ofthe pregnant woman as a function of wavelength.

FIG. 7C depicts a graph 702 that shows difference in absorptivitiesbetween oxy- and deoxy-state of fetal and the pregnant woman'shemoglobin in the near infrared (NIR) wavelengths of light from 700 nmto 1000 nm wherein the green dashed line represents the difference inabsorptivities between oxy- and deoxy-state of fetal hemoglobin as afunction of wavelength and the red dashed line represents the differencein absorptivities between oxy- and deoxy-state of fetal hemoglobin ofthe pregnant woman as a function of wavelength.

As can be seen in FIGS. 7A-7C, the greatest difference inabsorbativities between the fetus and the pregnant woman occur withinthe wavelength ranges of approximately 700-750 nm and 950-1000 nm. Thus,emission of infrared light in these wavelength ranges by fetalhemoglobin probe 115 is preferred so as to achieve optimaldifferentiation between the signal from the pregnant woman's hemoglobinand the fetus' hemoglobin.

All of the signal processing and analysis techniques described hereinmay employ one or more noise reduction techniques including, but notlimited to, cancelling out of ambient noise as may occur from lights inthe room where the pregnant mammal is located and the operation ofelectrical equipment near the pregnant mammal. Noise cancellingtechniques may also include looking for non-periodic modulations of theelectronic reflected signal and cancelling such modulations from thesignal because it is unlikely that a non-periodic contribution to thesignal is indicative of blood flow for either the pregnant mammal or thefetus.

Additionally, or alternatively, one or more of signal processing andanalysis techniques described herein may be combined with one another.For example, an electronic reflected signal may be processed usingprocess 401 and 402 so as to isolate the portion of the electronicreflected signal reflected by the fetus.

FIG. 8A provides an exemplary display 800 that provides a level of fetalhemoglobin oxygen saturation along with other information regardingmeasurements of the pregnant mammal and fetus. Display 800 provides afetal hemoglobin oxygen saturation level 805 that is, for example,expressed as a percentage of 100, a continuous waveform (i.e., aplethysmogram) that represents the fetal heart rate over time 810, and anumerical value representing fetal heart rate represented in beats perminute 815. Display 800 also provides, the pregnant mammal's hemoglobinoxygen saturation level 820 that is, for example, expressed as apercentage of 100, a continuous waveform that represents the pregnantmammal's heart rate over time 825, a numerical value representing thepregnant woman's heart rate represented in beats per minute 830. Display800 further provides a graph showing fetal heart rate over time asmeasured in hours 835, and an indication of uterine tone or pressuregenerated by uterine contractions as measured over time as measured inmmHG vs. time in minutes is provided as numerical value 845. The fetalheart rate over time graph 835 enables a physician to visually assesshow the fetal heart rate changes during uterine contractions and maydetermine how well the fetus is tolerating the labor and deliveryprocess. Uterine contraction numerical value 845 is a number from 0-50calculated by a pressure sensor and it allows the physician to assesshow long contractions are lasting, the intensity of the contractions,and the frequency of the contractions.

FIG. 8B provides an exemplary display 801 of synchronized fetalheartbeat, fetal hemoglobin oxygen saturation rate, and uterine tone forcorresponding moments in time. Display 801 is provided on a paper tapethat has a Cartesian grid printed thereon with the vertical linesrepresenting the passage of time (e.g., each vertical line represents aminute) and horizontal lines indicating a measurement scale. Paper tapeof this type is not printed with a specific time scale as these tapesare typically used continuously through a monitoring period that maylast many hours so, starting a time scale at 1, and progressing to 2, 3,4, etc. is not relevant to the information being provided to thephysician attending the pregnant mammal.

The upper graph of display 801 provides a graph of fetal heart rate asmeasured in beats per minute over time 860. The second graph of display801 provides a graph of fetal hemoglobin oxygen concentration (termed“fetal oxygen” for brevity's sake on the graph) over time 865. The thirdgraph of display 801 provides a graph of uterine tone (termed“contractions” for brevity's sake on the graph) 870. All three of graphs860, 865 and 870 are synchronized in the time domain so that ameasurement of fetal heartbeat for a particular moment in timecorresponds with the fetal hemoglobin oxygen concentration level and theuterine tone at that particular moment in time. In this way, theattending doctor (or other medical professional) can simultaneouslymonitor pregnant mammal's uterine tone, the fetus' heartbeat and thefetus' hemoglobin oxygen concentration level during, for example, thelabor and delivery process, to assess the health of the fetus.

Hence, systems, devices, and methods for determining fetal oxygen levelhave been herein disclosed. In some embodiments, use of the systems,devices, and methods described herein may be particularly useful duringthe labor and delivery of the fetus (e.g., during the first and/orsecond stage of labor) because it is difficult to assess fetal healthduring the labor and delivery process.

I claim:
 1. A method for determining a fetal hemoglobin oxygensaturation level comprising: projecting light of a first wavelength intothe abdomen of a pregnant mammal toward a fetus contained therein;projecting light of a second wavelength into the abdomen of the pregnantmammal toward the fetus; calculating, by a processor, a modulation ratiousing information derived from projecting the light of the first andsecond wavelengths; receiving a signal from a pulse oximetry probe ofthe pregnant mammal to determine an oxygen saturation level of thepregnant mammal's arterial blood; and determining the fetal hemoglobinoxygen saturation level using said oxygen saturation level of thepregnant mammal's arterial blood and the modulation ratio.
 2. The methodof claim 1, wherein a first light source emits the first wavelength anda second light source emits the second wavelength, the first wavelengthbetween 700 nm and 740 nm and the second wavelength between 800 nm and900 nm.
 3. The method of claim 1, further comprising: facilitating, bythe processor, provision of an indication of the fetal hemoglobin oxygensaturation level to an operator.
 4. The method of claim 1, furthercomprising: placing the pulse oximetry probe on a hand and/or finger ofthe pregnant mammal.
 5. A method for determining a fetal hemoglobinoxygen saturation level comprising: projecting light of a firstwavelength into the abdomen of a pregnant mammal toward a fetuscontained therein; projecting light of a second wavelength into theabdomen of the pregnant mammal toward the fetus; projecting light of athird wavelength directed toward the abdomen of the pregnant mammaltoward the fetus in order to account for the depth of fetus of thepregnant mammal; calculating, by a processor, a modulation ratio usinginformation derived from projecting the light of the first wavelengthand the second wavelength; and determining the fetal hemoglobin oxygensaturation level by using a curve that relates the modulation ratio tofetal hemoglobin oxygen saturation level.
 6. The method of claim 5,wherein a first light source emits the first wavelength and a secondlight source emits the second wavelength, the first wavelength between700 nm and 740 nm and the second wavelength between 800 nm and 900 nm.7. The method of claim 6, wherein a third light source emits the thirdwavelength.
 8. The method of claim 5, further comprising: facilitating,by the processor, provision of an indication of the fetal hemoglobinoxygen saturation level to an operator.
 9. A system for determining afetal hemoglobin oxygen saturation level comprising: a first lightsource adapted to project light of a first wavelength into the abdomenof a pregnant mammal toward a fetus contained therein; a second lightsource adapted to project light of a second wavelength into the abdomenof the pregnant mammal toward the fetus; a pulse oximetry probe; aprocessor, the processor being configured to: calculate a modulationratio using information derived from projecting the light of the firstand second wavelengths; using a signal from received from the pulseoximetry probe to determine an oxygen saturation level of the pregnantmammal's arterial blood; and determine the fetal hemoglobin oxygensaturation level using said oxygen saturation level of the pregnantmammal's arterial blood.
 10. The system of claim 9, wherein the firstwavelength is between 700 nm and 740 nm and the second wavelength isbetween 800 and 900 nm.
 11. The system of claim 9, the processor furtherconfigured to: facilitate provision of an indication of the fetalhemoglobin oxygen saturation level to an operator.
 12. The system ofclaim 9, wherein the pulse oximetry probe is adapted to be placed on ahand and/or finger of the pregnant mammal.
 13. The system of claim 9,further comprising: a housing configured to house the first lightsource, the second light source, a detector, a transceiver, and a powersource.